Abstract [en]

Extreme weather events can be expected to increase in frequency in the future. Our knowledge on how this may affect species persistence is, however, very limited. For reliable projections of future persistence we need to understand how extreme weather affects species' population dynamics.We analysed the effect of extreme droughts on the host plant Succisa pratensis, colonization-extinction dynamics, and future persistence of the threatened marsh fritillary Euphydryas aurinia. Specifically, we studied a metapopulation inhabiting a network of 256 patches on Gotland (Sweden), where the summer of 2018 was the driest ever recorded. We analysed how the frequency and leaf size of host plants changed between 2017 and 2019, based on 6,833 records in 0.5-m(2) sample plots. Using turnover data on the butterfly from 2018 to 2019 we modelled local extinction and colonization probabilities. Moreover, we projected future population dynamics with an increasing frequency of extreme years under three different management strategies that regulate the grazing regime.Our results show a substantial decrease in both frequency (46%) and size (20%) of host plants due to the drought, which taken together may constitute a 57% loss of food resources. The butterfly occupancy decreased by over 30% between 2018 and 2019 (from 0.36 to 0.27). The extinction probability increased with increasing 'effective area' of the patch (taking quality reduction due to grazing into account), and the colonization probability increased with increasing connectivity and ground moisture.Projections of future dynamics showed an increasing risk of metapopulation extinction with increasing frequency of years with extreme droughts. The risk, however, clearly differed between management strategies. Less grazing in years with droughts decreased the extinction risk considerably.Synthesis and applications. Extreme weather events can have profound negative impacts on butterflies and their host plants. For the marsh fritillary, an increased frequency of extreme droughts can lead to extinction of the entire metapopulation, even in a large and seemingly viable metapopulation. Increased grazing, due to fodder deficiency in dry years, may lead to cascading negative effects, while active management that reduce grazing in years with droughts can almost completely mitigate these effects.

Abstract [en]

Biodiversity can be characterised across several dimensions, which are crucial for the evaluation of ecosystem services. Functional diversity, a key aspect of biodiversity, provides a more realistic characterisation of the functioning of ecological communities than only studying their taxonomic diversity. The relevance of functional ecology studies has steadily increased in agroecosystems. However, the combined effects of pesticides and land cover heterogeneity on the taxonomic and functional diversity of arthropod communities have been studied less frequently. We sampled arthropods during the dry season in 19 rice fields located in two different regions of Northern Vietnam. We assorted the arthropods into functional groups corresponding to different feeding habits and calculated the taxonomic and functional group diversifies. Finally, we analysed the impacts of pesticide applications and land cover heterogeneity on both diversity measures. Taxonomic and functional group diversity measures were highly correlated. In turn, both diversity measures responded similarly to land cover heterogeneity and pesticides. Land cover heterogeneity had positive effects on taxonomic and functional group diversity, mainly at the early stage of rice crops. Conversely, the impact of pesticide application on both diversity measures was strongly negative. Our results suggest that rice agroecosystems can be more sustainable by increasing landscape heterogeneity and a reduced pesticide use. Such schemes may help to maintain higher levels of biodiversity that ensure ecosystem functioning, which will be therefore likely beneficial to provide ecosystem services in agroecosystems.

Kunin, William E.

Abstract [en]

Atmospheric nitrogen deposition and other sources of environmental eutrophication have increased substantially over the past century worldwide, notwithstanding the recent declining trends in Europe. Despite the recognized susceptibility of plants to eutrophication, few studies evaluated how impacts propagate to consumers, such as pollinators. Here we aim to test if soil eutrophication contributes to the temporal dynamics of pollinators and their larval resources. We used a temporally and spatially explicit historical dataset with information on species occurrences to test if soil eutrophication, and more specifically nitrogen deposition, contributes to the patterns of change of plant and pollinator richness in the Netherlands over an 80 yr period. We focus on bees and butterflies, two groups for which we have good knowledge of larval resources that allowed us to define groups of species with different nitrogen related diet preferences. For each group we estimated richness changes between different 20-yr periods at local, regional and national scale, using analytical methods developed for analyzing richness changes based on collection data. Our findings suggest that the impacts of soil eutrophication on plant communities propagate to higher trophic levels, but with a time-lag. Pollinators with nitrogen-related diet preferences were particularly affected, in turn potentially impairing the performance of pollinator-dependent plants. Pollinator declines continued even after their focal plants started to recover. In addition, our results suggest that current levels of nitrogen deposition still have a negative impact on most groups here analyzed, constraining richness recoveries and accentuating declines. Our results indicate that the global increase in nitrogen availability plays an important role in the ongoing pollinator decline. Consequently, species tolerances to soil nitrogen levels should be considered across all trophic levels in management plans that aim to halt biodiversity loss and enhance ecosystems services worldwide.

Abstract [en]

Animal colour patterns long have provided information about key processes that drive the ecological and evolutionary dynamics of biological diversity. Theory and empirical evidence indicate that variation in colour patterns and other traits among individuals generally improves the performance of populations and species, for example by reducing predation risk, increasing establishment success, improving resilience to environmental change, and decreasing risk of extinction. However, little is known about whether and how variation in colour pattern among species is associated with variation in other phenotypic dimensions. To address this issue, we analysed associations of colour pattern with morphological, behavioural and life-history traits on the basis of data for nearly 400 species of noctuid moths. We found that moths with more variable colour patterns had longer flight activity periods, more diverse habitats and a greater number of host plant species than species with less variable colour patterns. Variable coloration in adult noctuid moths therefore can be considered as indicative of broader niches and generalist diets. Colour pattern variability was not significantly associated with overwintering stage or body size (wing span), and it was independent of whether the colour pattern of the larvae was non-variable, variable or highly variable. Colour pattern variation during the larval stage tended to increase as the duration of the flight activity period increased, but was independent of the length of the larval period, diet breadth and habitat use. The realization that information on colour pattern variation in adult moths, and possibly other organisms, offers a proxy for niche breadth and dietary generalization can inform management and conservation biology.

Abstract [en]

Grazing generally benefits grassland biodiversity as it prevents shrub and tree succession. However, too intense grazing may have negative effects for example many grassland insects. EU-subsidies for grazing of some habitats, aimed at promoting biodiversity, still require a relatively intense grazing, and could therefore have negative consequences for some species. We quantified how such grazing affects habitat quality for the marsh fritillary butterfly, and how this influence its colonization-extinction dynamics and persistence. Specifically, we studied a metapopulation on Gotland (Sweden), where the marsh fritillary occupies unfertilized calcareous grassland with a naturally slow succession. We quantified the difference in larvae autumn nests between grazed and ungrazed habitat, and used this difference to adjust the 'effective area' of 256 habitat patches in a 50 km(2) landscape. We then parameterized a metapopulation model based on the occurrence pattern of the adult butterfly, and simulated future population development under different grazing regimes. The results showed that ungrazed habitat harbored 4.8 times more nests than grazed habitat. Reducing the 'effective area' of grazed patches accordingly increased the local extinction probability and decreased colonization. Grazing all suitable habitat reduced the occupancy by over 80%, while no grazing increased the occupancy by up to 40%, based on projections of future dynamics. Current grazing is clearly too intense, and EU-subsidies are here, thus, a conservation measure with negative consequences for a threatened butterfly. To prevent this, subsidies for grazing need to be more flexible and better adapted to the prevailing soil conditions and requirements of the target species.

Abstract [en]

A high capacity for long‐distance dispersal is a key to success for species confronted with environmental heterogeneity, habitat modification, fragmentation and loss. However, dispersal capacity is difficult to quantify and therefore poorly known in most taxa. Here, we report on a test for an association of variation in dispersal capacity with variable colouration of noctuid moths. First, using data from 12 experienced lepidopterologists, we showed that despite variation among experts in average assessments, different species are consistently classified as having non‐variable, variable or highly variable colour patterns when assessed by different experts. We then compared the incidence of non‐resident species with high inter‐individual variation in colour patterns recorded on the isolated island Utklippan (n = 47), with that in a species pool of potential long‐distance dispersers from the nearest mainland (n = 295). Species with high inter‐individual colour pattern variation were over‐represented on the island compared with species having non‐variable colouration. This finding constitutes rare evidence from the wild of long‐distance dispersal, measured on a spatial scale relevant for moths when tracking habitats in fragmented and changing landscapes or when keeping pace with environmental challenges associated with climate change. Finally, we showed that Swedish noctuid moths classified as agricultural pests (n = 28) had more variable colour patterns compared with non‐pests (n = 368). The majority of agricultural pests were also recorded on the isolated island, an outcome that is indicative of pest species having high dispersal capacity. Data on colour pattern variation may thus offer a simple and cost‐effective proxy to estimate dispersal capacity and can also help identify potential pest species. Our findings are potentially useful when modelling and predicting population and range dynamics of species in spatiotemporally heterogeneous environments, with direct implications for conservation biology and pest management.

Abstract [en]

Pollination of wild and crop plants by animal pollinators is a key ecosystem service that is important to human welfare. Across Europe, climatic conditions are the most important drivers of occurrence and richness of pollinators followed by land cover and soil conditions. However, the example of recent range shifts of important pollinators such as the bumblebees shows that northern range expansions can be limited while southern range contractions can be considerable, leading to severe consequences under future scenarios. The way we utilize our landscape is a likely reason for such strong effects since the response to changing temperature conditions strongly depends on the amount of semi-natural area available in a landscape. In particular, the number of bee species is less sensitive to increasing temperatures when the amount of semi-natural habitat is high, while species richness drastically declines in intensively used agricultural landscapes and even more so with increasing temperatures. Such interactive effects of major drivers of global change bear a big chance for enhancing resilience in pollinator communities and thus in food production systems, e.g. by increasing the amount of semi-natural habitat as is the goal of the EU strategy for Green Infrastructure and some of the regulations in the EU Common Agricultural Policy (CAP).

Helm, Aveliina

Abstract [en]

Recently developed glacier forelands provide valuable insights into vegetation dynamics. We studied the vascular plants in the glacier forelands of the Almajallojekna glacier in comparison to the plants in the surrounding area. The glacier is retreating rapidly at an average rate of 0.17 km(2) per year from 1898 to 2012. In the newly emerged glacier forelands, we found that 32 percent of the 381 plant taxa occurred in the surrounding region. Sixty-eight plant species were present on the youngest terrain (0-31 y), an additional thirteen species occurred on terrain aged 32-53 years, and an additional forty-two species were detected on terrain aged 54-114 years. Of the surrounding species pool, plant species that had successfully established in recently deglaciated terrains were characterized by high regional abundance and low seed weight, and they were more likely to be members of the plant families Saxifragaceae, Salicaceae, and Asteraceae. Woody plant species with a preference for well-drained soils were more likely to be present in the youngest terrain. Our results show that the vegetation of glacier forelands is developing rapidly depending on the plant species in the surrounding area and the species' life-history traits.

Abstract [en]

It has been hypothesized that species with more variable color patterns should have higher establishment success and be less sensitive to environmental changes and local extinction compared with species that do not vary in color. This difference in colonization/extinction balance should manifest as larger continental range distributions and modulate the species-area relationship on true islands. We evaluated these predictions using data for 1216 species of butterflies and moths that differed with regard to inter-individual variation in color pattern. We show that species with more variable color patterns have larger continental range sizes in Europe compared with non-variable species. We also provide rare evidence that the slope of the species-area relationship on islands is steeper for species having non-variable color patterns, suggesting that to preserve 60% of non-variable species would require an area twice as large compared to what would be needed to preserve 60% of variable species. Our findings suggest that combining information on ecological characteristics with presence/absence data from small and medium sized islands can help identify traits that drive species range patterns at the continental scale, and that individual variation in color pattern can be used as a proxy for ecological generalization and the ability to cope with environmental change.